Narrator: Listen to part of a lecture in an environmental science class. Professor: Today we're going to talk about a surprising solution to urban flooding: green roofs. Now, a green roof is essentially a layer of vegetation planted on a rooftop. But it's not just for looks. The key is the growing medium, the soil-like layer. When it rains, this porous material absorbs water like a sponge, slowing down the runoff. In a typical city, rain hits impervious surfaces like concrete and immediately flows into storm drains, which can quickly overwhelm the system. Green roofs, however, retain a significant portion of rainfall, releasing it slowly over hours. Some studies show they can hold up to 70% of a heavy storm's water. So, by installing green roofs on a wide scale, cities could reduce the peak flow into their drainage systems, lowering flood risk. There are other benefits too—insulation and habitat for insects—but the flood mitigation aspect is particularly compelling for urban planners.
❓ Câu hỏi What is the main reason the professor discusses green roofs as a solution to urban flooding?
A. They absorb and slowly release rainwater, reducing strain on drainage systems.
B. They are cheaper to install than traditional concrete roofs.
C. They provide habitats for urban wildlife, which helps with water purification.
D. They completely eliminate the need for storm drains in cities.
✅ Đáp án đúng
They absorb and slowly release rainwater, reducing strain on drainage systems.
TOEFL Listening Tips
Skim the questions first to predict the content
Watch for signal words in lectures and conversations (however, actually, in fact)
For main idea questions, focus on the beginning; for detail questions, focus on examples and data
For attitude questions, pay attention to the speaker's tone and word choice
Take notes on keywords; don't try to write down every word
